1. Field of the Invention
The present invention relates generally to a storage medium for an ultra-high density data storage device.
2. Description of the Related Art
Recently, scientists have been developing alternative ultra-high-density data storage devices and techniques useful for operating ultra-high-density data storage devices. These devices and techniques store data bits within storage regions sized on the nanometer scale and possess advantages over conventional data storage devices. Among these advantages are quicker access to the data bits, a lower cost per bit and enablement of the manufacturing of smaller electronic devices.
FIG. 1 illustrates an ultra-high-density data storage device configuration according to the related art. This configuration includes a storage medium 1 that is separated into many storage regions. These storage regions are illustrated as squares on the storage medium 1 and are each capable of storing one data bit.
Two types of storage regions are illustrated in FIG. 1. One type includes unmodified regions 2 that typically store data bits representing the value “0”. The other type includes modified regions 3 that typically store data bits representing the value “1”. Typical periodicities between any two storage regions range between 1 and 100 nanometers
FIG. 1 also illustrates, conceptually, emitters 4, positioned above the storage medium 1, and a gap between the emitters 4 and the storage medium 1. The emitters 4 are capable of emitting electron beams and are arranged on a movable emitter array support 5 (also known as a “micromover”) that can hold hundreds or even thousands of emitters 4 in a parallel configuration. The emitter array support 5 provides electrical connections to each emitter 4, as illustrated conceptually by the wires on the top surface of emitter array support 5.
The emitter array support 5 can move the emitters 4 with respect to the storage medium 1, thereby allowing each emitter 4 to scan across many storage regions on the storage medium 1. Alternatively, the storage medium 1 can be placed on a platform that moves the storage medium 1 relative to the emitter array support 5. Movement of the platform can be actuated electrostatically, magnetically or by the use of piezoelectrics. However, regardless of whether the support 5 or the storage medium 1 moves, the range of motion of the emitter array support 5 relative to the storage medium 1 can be large enough to allow each emitter 4 to travel across and to have access to data bits in tens of thousands or even millions of data storage regions.
As an emitter 4 moves relative to the storage medium 1, the emitter 4 can bombard a nanometer-scaled storage region on the surface of the storage medium 1 with either a high-power-density or a low-power-density electron beam. When a high-power-density beam is emitted, the beam can locally alter the material characteristics of the bombarded region. For example, the high-power-density beam can create defects in the bombarded region or can locally heat up a crystalline region such that the region later cools into an amorphous state of the same material. By these and other processes, the phase of the bombarded region can be changed and the emitter 4 can write “1” data bits to the storage medium 1.
When a low-power-density electron beam is emitted, the beam no longer has enough power to alter the material characteristics or state of the bombarded region. Hence, a writing operation does not take place. Instead, a reading operation can take place by monitoring the path of the electrons in the beam or the effect of the electrons in the beam on the bombarded region. As will be discussed below, monitoring the path of the electrons and/or the interactions of the electrons with the bombarded region allows for a determination to be made as to whether or not the low-power-density beam is bombarding a region of the storage medium 1 that has previously been “written to” and now contains a “1” data bit.
Specifically, in order to determine whether a “1” data bit or a “0” data bit is being bombarded, several options exist. One of these options, which proves useful when “1” data bits include an amorphous material and “0” data bits include the same material in a crystalline phase, involves monitoring the number of beam electrons that are backscattered from the bombarded region over time.
Since amorphous and crystalline phases of the same materials have different backscattered electron coefficients (BECs), different numbers of electrons are backscattered by “1” and “0” data bits in the storage medium 1 when the same low-power-density beam bombards each data bit. Hence, by monitoring the number of electrons backscattered from a given region as it is being bombarded by a low-power-density electron beam, it is possible to determine whether the region contains a “0” data bit or a “1” data bit.
Some specific embodiments of the ultra-high-density data storage device discussed above are disclosed in U.S. Pat. No. 5,557,596 to Gibson et al. (Gibson '596), the contents of which are incorporated herein in their entirety by reference. In addition to discussing the backscattered electron reading technique and the technique that involves writing amorphous data bits in a crystalline storage medium 1, the Gibson '596 patent also discusses a variety of other writing and reading methods.